Hybrid electric vehicles are a new generation of new energy vehicles that are powered by traditional internal combustion engines and electric motors. They have the advantages of low emissions, low fuel consumption and high power output. According to the power ratio of the motor and the traditional internal combustion engine, it can be divided into strong mixing, medium mixing and weak mixing.
The 48V BRS (Boost Recupera TIon system) system, as one of the hybrid hybrid electric vehicle (mHEV), will be the most cost-effective new energy vehicle technology solution in the next decade. Compared with the traditional internal combustion engine, the 48V BRS system mainly adds 48V Boost Recupera (BRM), 48V/12V DC power converter (PCU, Power Conversion Unit) and 48V lithium battery. , energy recovery, acceleration assistance, electric crawling and other functions. The traditional internal combustion engine vehicle is equipped with the first generation 48V system (the motor is integrated with the engine through the pulley). The fuel saving rate is 8~12%. The second generation 48V system (motor and gearbox integration) is expected to have a fuel saving rate of 12~19%.
The origin of one, 48 volts
1) What is 48 volts?
48 volts refers to the system rated DC voltage, not always stable at 48V; according to the LV148 definition as shown below:
The 48 volt battery voltage will vary with the SOC (remaining battery capacity), for example, the SOC is 10% to 100% at normal temperature, and the open circuit voltage is 32.5V to 49.8V;
The power assist and energy recovery mode of the BRM motor will also cause the voltage of 48V to rise or fall. When the battery SOC is high, the battery is charged, and the required voltage is often higher than 50V.
The DC voltage is not a straight line and is fluctuating. Regarding the allowable fluctuation of the DC voltage, the European regulations stipulate that the effective value of the fluctuation part (ie, the equivalent value after the mean value is removed) is less than 10% of the voltage average, which is regarded as DC. Voltage;
2) Why is 48V?
60V is a safe voltage. According to the above mentioned 10% margin, the maximum voltage allowed by the system is 54V. Consider the battery voltage change and energy recovery mode mentioned in 1), the voltage will rise, and then stay. A certain margin becomes 48V.
The origin of the 48V name may also have some historical reasons.
Second, 48 volt key components
The typical connection diagram of the 48V BRS electrical network is as follows. In addition to BRM motors, DC converters, 48 ​​volt batteries and other major components, the 48V electrical load concept products on the market are also common, such as 48V electric supercharger, 48V electric heating catalyst, etc., the function expansion and promotion of 48V system Also has a positive effect.
1) Power recovery motor (BRM)
The typical power recovery motor is shown in the figure below. It can be used to generate electricity, and it can also provide forward power for the vehicle. It can even start the engine quickly with a 48 volt battery pack. BRM generally uses claw pole motors, which replace traditional 14 volt generators.
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